An optical gyroscope measures the interference pattern generated by two light beams, traveling in opposite directions within a mirrored ring (laser or “ring laser” gyroscopes) or fiber loop (fiber optic gyroscopes), in order to detect very small changes in motion. Optical gyroscopes are based on a principle called the “Sagnac effect” discovered at the beginning of the 20th century. Optical gyroscopes have a variety of applications, but are particularly well suited for use in guidance, navigation, and control systems such as those of aircrafts and spacecrafts. An example of an optical gyroscope can be found in U.S. Pat. No. 4,545,682, incorporated herein by reference in its entirety.
There are several different types of fiber optic gyroscopes including at least interferometer fiber optic gyroscopes (IFOGs) and resonator fiber optic gyroscopes (RFOGs). IFOGs are phase sensitive devices with the Sagnac effect generating an optical phase difference between two counterpropagating waves in a rotating fiber coil. RFOGs are frequency sensitive devices with the Sagnac effect generating a frequency difference between two resonant beams in a ring fiber cavity locked to resonant clockwise and counterclockwise frequencies.
IFOGs typically operate in either an open loop or a closed loop configuration. In the closed loop configuration, a phase shift equal in magnitude but opposite in sign to the phase shift generated by the Sagnac effect is generated, and the frequency of the generated phase shift is then determined from the apparatus generating it.
In many instances a FOG will comprise a optical receiver or other mechanism for converting the light output (which is a combination of the two counterpropogating beams) by a coil assembly to an analog signal. As the term is used herein, the “optical power” of the gyroscope is a measurement of the power of the light being output by the coil assembly and fed into the optical receiver.